1. Field of the Invention
The invention relates generally to a vehicle assembly line, and more specifically to a vehicle underbody assembly line.
2. Description of the Related Art
For example, Japanese Patent Application Publication No. 2009-1182 (JP-A-2009-1182) describes a technology related to a vehicle assembly line for producing vehicles such as automobiles.
As shown in FIG. 15A, in a vehicle assembly line 100 described in JP-A-2009-1182, multiple vehicle bodies 110 are conveyed along the assembly line. More specifically, the vehicle bodies 110 are supported by respective floor friction carriers 120, and the floor friction carriers 120 aligned along the conveyance direction (direction in which the vehicle bodies 110 are moved down the vehicle assembly line 100) are moved along the conveyance direction. In accordance with the movement of the floor friction carriers 120, the vehicle bodies 110 are conveyed. In this case, because the vehicle bodies 110 are supported in such a manner that the longitudinal direction (see an arrow A in FIG. 15A) of the vehicle bodies 110 is parallel to the conveyance direction, the vehicle bodies 110 are conveyed with the longitudinal direction of the vehicle bodies 110 kept parallel to the conveyance direction.
Usually, a worker fits vehicle underbody parts to each of vehicle bodies that move down a vehicle assembly line (performs a fitting work). The worker sequentially performs this fitting work on the vehicle bodies that are conveyed from the upstream side. When fitting the vehicle underbody parts to each vehicle body, the worker fits the vehicle underbody parts to the vehicle body from below the vehicle body. For example, when the worker fits a vehicle underbody part A to a vehicle body a with the use of a tool X, fits a vehicle underbody part B to the vehicle body a with the use of a tool Y, and fits a vehicle underbody part C to the vehicle body a with the use of a tool Z, the worker performs a work 1) in which the worker goes get the vehicle underbody part A and the tool X and then fits the vehicle underbody part A to the vehicle body α. When fitting of the vehicle underbody part A is completed, the worker performs a work 2) in which the worker goes get the vehicle underbody part B and the tool Y and then fits the vehicle underbody part B to the vehicle body α. When fitting of the vehicle underbody part B is completed, the worker performs a work 3) in which the worker goes get the vehicle underbody part C and the tool Z and then fits the vehicle underbody part C to the vehicle body α. The worker sequentially performs the works 1) to 3). When performing these works, the worker fits the vehicle underbody parts A, B and C from below the vehicle body α. Therefore, if the tools X, Y and Z and the vehicle underbody parts A, B and C are located under the vehicle body α, it is possible to minimize the distance between the worker, and the tools X, Y and Z and the vehicle underbody parts A, B and C. As a result, it is possible to efficiently perform the fitting works on the vehicle body α. That is, if the tools used to fit the vehicle underbody parts to the vehicle body (hereinafter, referred to as “tools”) and the vehicle underbody parts are located under the vehicle body when the vehicle underbody parts are fitted to the vehicle body, it is possible to efficiently perform the works for fitting the vehicle underbody parts to the vehicle body.
In some cases, the tools are placed on a tool wagon in advance, the worker selects a necessary tool depending on the type of a vehicle underbody part, and uses the selected tool to fit the vehicle underbody part to the vehicle body. If the tool wagon is located under the vehicle body when the vehicle underbody parts are fitted to the vehicle body, it is possible to minimize the distance between the worker and the tools. As a result, it is possible to efficiently perform the works for fitting the vehicle underbody parts to the vehicle body. The worker uses the same tools to fit the vehicle underbody parts to each of the vehicle bodies that are sequentially conveyed. Therefore, if it is possible to form a path along which the tool wagon is conveyed (hereinafter, referred to as “conveyance path”) and which connects the spaces under the vehicle bodies to each other, the tool wagon is moved along the conveyance path. As a result, the tool wagon moves under the vehicle bodies. Thus, the tool wagon is located under the vehicle body when the vehicle underbody parts are fitted to the vehicle body. In addition, it is possible to fit the vehicle underbody parts to the vehicle bodies with the use of the same tools.
If the vehicle underbody parts are located under the vehicle body when the vehicle underbody parts are fitted to the vehicle body, it is possible to minimize the distance between the worker and the vehicle underbody parts. As a result, it is possible to efficiently perform the works for fitting the vehicle underbody parts to the vehicle body. In recent yeas, the types of vehicle underbody parts vary depending on the types of vehicles (types of vehicle bodies) due to diversification of the types of vehicles. Therefore, in order to minimize occurrence of an error in selection of vehicle underbody parts when the vehicle underbody parts are fitted to the vehicle body and to make it easier to deal with various types of vehicles, a set of vehicle underbody parts for each one of the vehicle bodies is prepared in advance, the vehicle bodies and the sets of vehicle underbody parts corresponding to the respective vehicle bodies are associated with each other, and then the vehicle bodies and the vehicle underbody parts are moved down the assembly line. Therefore, if a space in which the vehicle underbody parts are placed (hereinafter, referred to as “part space”) is formed under each vehicle body, a set of vehicle underbody parts for each one of the vehicle bodies is placed under the vehicle body in advance, the vehicle bodies and the sets of vehicle underbody parts corresponding to the respective vehicle bodies are associated with each other, and then the vehicle bodies and the vehicle underbody parts are moved down the assembly line. Thus, the set of vehicle underbody parts is located under the corresponding vehicle body when the vehicle underbody parts are fitted to the vehicle body.
As described above, if the conveyance path is formed in the vehicle assembly line and the part space is formed under each vehicle body, the tools and the vehicle underbody parts may be located under the vehicle body when the vehicle underbody parts are fitted to the vehicle body. As a result, it is possible to efficiently perform the works for fitting the vehicle underbody parts to the vehicle body. In order to avoid the situation where the tool wagon hits the vehicle underbody parts when the tool wagon is moved, the conveyance path and the each part space need to be formed so as not to overlap with each other.
As shown in FIGS. 15A and 15B, in the vehicle assembly line 100 described in JP-A-2009-1182, a conveyance path 130 that connects the spaces under the vehicle bodies 110 to each other in the conveyance direction is formed, and part spaces are formed under the vehicle bodies 110. In this case, because the vehicle bodies 110 are conveyed with the longitudinal direction of the vehicle bodies 110 kept parallel to the conveyance direction, the conveyance path 130 is the space that connects the spaces under the vehicle bodies 110 to each other in the longitudinal direction of the vehicle bodies 110. Thus, in order to form the part space under each vehicle body 110 separately from the conveyance path 130, the part space need to be offset from the conveyance path 130 in the lateral direction of the vehicle body 110 (the direction perpendicular to the longitudinal direction of the vehicle body 110, for example, the direction of an arrow B in FIG. 15B). However, the lateral length of the vehicle body does not greatly vary depending on the types of vehicle bodies, and is usually set to a value that is within a range from 1700 mm to 1800 mm and that is obviously shorter than the longitudinal length of the vehicle body. Accordingly, if the conveyance path 130 is formed, it is difficult to form the part space under each vehicle body 110. With the technology described in JP-A-2009-1182, it is difficult to sufficiently meet the demand to locate the tool and the vehicle underbody parts under the vehicle body when the vehicle parts are fitted to the vehicle body, and, consequently, it is difficult to contribute to an improvement in the efficiency of the works for fitting the vehicle underbody parts to the vehicle body.